[PATCH 09/39] scsi: do not manipulate device reference counts in scsi_get/put_command

Christoph Hellwig
2014-03-17T13:27:42Z

[-- Attachment #1: 0009-scsi-do-not-manipulate-device-reference-counts-in-sc.patch --]
[-- Type: text/plain, Size: 6465 bytes --]

Many callers won't need this and we can optimize them away. In addition
the handling in the __-prefixed variants was inconsistant to start with.

Based on an earlier patch from Bart Van Assche.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
drivers/scsi/scsi.c | 37 ++++++++++++-------------------------
drivers/scsi/scsi_error.c | 6 ++++++
drivers/scsi/scsi_lib.c | 12 +++++++++++-
drivers/scsi/scsi_tgt_lib.c | 3 ++-
include/scsi/scsi_cmnd.h | 3 +--
5 files changed, 32 insertions(+), 29 deletions(-)

diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index fb86479..2b12983 100644
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -284,27 +284,19 @@ EXPORT_SYMBOL_GPL(__scsi_get_command);
*/
struct scsi_cmnd *scsi_get_command(struct scsi_device *dev, gfp_t gfp_mask)
{
- struct scsi_cmnd *cmd;
+ struct scsi_cmnd *cmd = __scsi_get_command(dev->host, gfp_mask);
+ unsigned long flags;

- /* Bail if we can't get a reference to the device */
- if (!get_device(&dev->sdev_gendev))
+ if (unlikely(cmd == NULL))
return NULL;

- cmd = __scsi_get_command(dev->host, gfp_mask);
-
- if (likely(cmd != NULL)) {
- unsigned long flags;
-
- cmd->device = dev;
- INIT_LIST_HEAD(&cmd->list);
- INIT_DELAYED_WORK(&cmd->abort_work, scmd_eh_abort_handler);
- spin_lock_irqsave(&dev->list_lock, flags);
- list_add_tail(&cmd->list, &dev->cmd_list);
- spin_unlock_irqrestore(&dev->list_lock, flags);
- cmd->jiffies_at_alloc = jiffies;
- } else
- put_device(&dev->sdev_gendev);
-
+ cmd->device = dev;
+ INIT_LIST_HEAD(&cmd->list);
+ INIT_DELAYED_WORK(&cmd->abort_work, scmd_eh_abort_handler);
+ spin_lock_irqsave(&dev->list_lock, flags);
+ list_add_tail(&cmd->list, &dev->cmd_list);
+ spin_unlock_irqrestore(&dev->list_lock, flags);
+ cmd->jiffies_at_alloc = jiffies;
return cmd;
}
EXPORT_SYMBOL(scsi_get_command);
@@ -313,10 +305,8 @@ EXPORT_SYMBOL(scsi_get_command);
* __scsi_put_command - Free a struct scsi_cmnd
* @shost: dev->host
* @cmd: Command to free
- * @dev: parent scsi device
*/
-void __scsi_put_command(struct Scsi_Host *shost, struct scsi_cmnd *cmd,
- struct device *dev)
+void __scsi_put_command(struct Scsi_Host *shost, struct scsi_cmnd *cmd)
{
unsigned long flags;

@@ -331,8 +321,6 @@ void __scsi_put_command(struct Scsi_Host *shost, struct scsi_cmnd *cmd,

if (likely(cmd != NULL))
scsi_pool_free_command(shost->cmd_pool, cmd);
-
- put_device(dev);
}
EXPORT_SYMBOL(__scsi_put_command);

@@ -346,7 +334,6 @@ EXPORT_SYMBOL(__scsi_put_command);
*/
void scsi_put_command(struct scsi_cmnd *cmd)
{
- struct scsi_device *sdev = cmd->device;
unsigned long flags;

/* serious error if the command hasn't come from a device list */
@@ -357,7 +344,7 @@ void scsi_put_command(struct scsi_cmnd *cmd)

cancel_delayed_work(&cmd->abort_work);

- __scsi_put_command(cmd->device->host, cmd, &sdev->sdev_gendev);
+ __scsi_put_command(cmd->device->host, cmd);
}
EXPORT_SYMBOL(scsi_put_command);

diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index 78b004d..771c16b 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -2288,6 +2288,11 @@ scsi_reset_provider(struct scsi_device *dev, int flag)
if (scsi_autopm_get_host(shost) < 0)
return FAILED;

+ if (!get_device(&dev->sdev_gendev)) {
+ rtn = FAILED;
+ goto out_put_autopm_host;
+ }
+
scmd = scsi_get_command(dev, GFP_KERNEL);
blk_rq_init(NULL, &req);
scmd->request = &req;
@@ -2345,6 +2350,7 @@ scsi_reset_provider(struct scsi_device *dev, int flag)
scsi_run_host_queues(shost);

scsi_next_command(scmd);
+out_put_autopm_host:
scsi_autopm_put_host(shost);
return rtn;
}
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index aa6a581..f8a77d8 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -95,6 +95,7 @@ static void scsi_unprep_request(struct request *req)
req->special = NULL;

scsi_put_command(cmd);
+ put_device(&cmd->device->sdev_gendev);
}

/**
@@ -529,6 +530,7 @@ void scsi_next_command(struct scsi_cmnd *cmd)
get_device(&sdev->sdev_gendev);

scsi_put_command(cmd);
+ put_device(&sdev->sdev_gendev);
scsi_run_queue(q);

/* ok to remove device now */
@@ -1116,6 +1118,7 @@ err_exit:
scsi_release_buffers(cmd);
cmd->request->special = NULL;
scsi_put_command(cmd);
+ put_device(&cmd->device->sdev_gendev);
return error;
}
EXPORT_SYMBOL(scsi_init_io);
@@ -1126,9 +1129,15 @@ static struct scsi_cmnd *scsi_get_cmd_from_req(struct scsi_device *sdev,
struct scsi_cmnd *cmd;

if (!req->special) {
+ /* Bail if we can't get a reference to the device */
+ if (!get_device(&sdev->sdev_gendev))
+ return NULL;
+
cmd = scsi_get_command(sdev, GFP_ATOMIC);
- if (unlikely(!cmd))
+ if (unlikely(!cmd)) {
+ put_device(&sdev->sdev_gendev);
return NULL;
+ }
req->special = cmd;
} else {
cmd = req->special;
@@ -1291,6 +1300,7 @@ int scsi_prep_return(struct request_queue *q, struct request *req, int ret)
struct scsi_cmnd *cmd = req->special;
scsi_release_buffers(cmd);
scsi_put_command(cmd);
+ put_device(&cmd->device->sdev_gendev);
req->special = NULL;
}
break;
diff --git a/drivers/scsi/scsi_tgt_lib.c b/drivers/scsi/scsi_tgt_lib.c
index 84a1fdf..e51add0 100644
--- a/drivers/scsi/scsi_tgt_lib.c
+++ b/drivers/scsi/scsi_tgt_lib.c
@@ -155,7 +155,8 @@ void scsi_host_put_command(struct Scsi_Host *shost, struct scsi_cmnd *cmd)
__blk_put_request(q, rq);
spin_unlock_irqrestore(q->queue_lock, flags);

- __scsi_put_command(shost, cmd, &shost->shost_gendev);
+ __scsi_put_command(shost, cmd);
+ put_device(&shost->shost_gendev);
}
EXPORT_SYMBOL_GPL(scsi_host_put_command);

diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h
index 91558a1..414edf9 100644
--- a/include/scsi/scsi_cmnd.h
+++ b/include/scsi/scsi_cmnd.h
@@ -142,8 +142,7 @@ static inline struct scsi_driver *scsi_cmd_to_driver(struct scsi_cmnd *cmd)
extern struct scsi_cmnd *scsi_get_command(struct scsi_device *, gfp_t);
extern struct scsi_cmnd *__scsi_get_command(struct Scsi_Host *, gfp_t);
extern void scsi_put_command(struct scsi_cmnd *);
-extern void __scsi_put_command(struct Scsi_Host *, struct scsi_cmnd *,
- struct device *);
+extern void __scsi_put_command(struct Scsi_Host *, struct scsi_cmnd *);
extern void scsi_finish_command(struct scsi_cmnd *cmd);

extern void *scsi_kmap_atomic_sg(struct scatterlist *sg, int sg_count,
--
1.7.10.4